High CT values relative to the brainstem differentiate inverted papillomas from nasal polyps

A diagnostic indicator for the differentiation of inverted papillomas (IPs) from inflammatory nasal polyps (NPs) has not been established. This study aimed to evaluate whether CT attenuation values relative to those of the brainstem (relative CT number) could be useful for differentiating IPs from NPs.

Consecutive patients who were pathologically diagnosed with IP or NP between 2005 and 2019 were retrospectively identified. Relative CT numbers were compared between the two patient groups. The factors with predictive power for differentiating IPs from NPs were identified by univariate and multivariate logistic regression analyses.

One hundred and twenty-two sinonasal masses were finally analysed (IP, 51 cases; NP, 71 cases). Relative CT numbers were significantly higher in IP than in NP (P < 0.001). Univariate logistic regression analysis showed relative CT number, bone erosion and bone thickening to have predictive value for differentiating IPs from NPs (relative CT number, P < 0.001; bone erosion, p = 0.04; bone thickening, P < 0.001). In the multivariate logistic regression analysis, relative CT number and bone thickening had predictive value for distinguishing IP from NP (relative CT number, p < 0.001; bone thickening, p = 0.02). The optimum cut off value calculation from the area under the receiver operating characteristics curve indicated that a relative CT number >1.3 was significantly associated with IP (sensitivity, 72.6%; specificity, 87.3%). Within cases not showing bone thickening, only the relative CT number was a predictive factor for differentiating IPs from NPs in the univariate analysis.

High relative CT numbers could potentially indicate IP, and their measurement could provide a basis for differentiating IPs from NPs.